U.S. patent application number 15/826147 was filed with the patent office on 2018-06-28 for method and apparatus for rapid sub-diffraction infrared imaging and spectroscopy and complementary techniques.
The applicant listed for this patent is Anaysis Instruments Corp.. Invention is credited to Kevin Kjoller, Craig Prater, Roshan Shetty.
Application Number | 20180180642 15/826147 |
Document ID | / |
Family ID | 62241875 |
Filed Date | 2018-06-28 |
United States Patent
Application |
20180180642 |
Kind Code |
A1 |
Shetty; Roshan ; et
al. |
June 28, 2018 |
METHOD AND APPARATUS FOR RAPID SUB-DIFFRACTION INFRARED IMAGING AND
SPECTROSCOPY AND COMPLEMENTARY TECHNIQUES
Abstract
Methods and apparatus for performing chemical spectroscopy on
samples from the scale of nanometers to millimeters or more with a
multifunctional platform combining analytical and imaging
techniques including atomic force microscopy, infrared
spectroscopy, confocal microscopy, Raman spectroscopy and mass
spectrometry. For infrared spectroscopy, a sample is illuminated
with infrared light and the resulting sample distortion is read out
with either a focused UV/visible light beam and/or AFM tip. Using
the AFM tip or the UV/visible light beam it is possible to measure
the IR absorption characteristics of a sample with spatial
resolution ranging from around 1 .mu.m or less to the nanometer
scale. The combination of both techniques provides a rapid and
large area survey scan with the UV/visible light and a high
resolution measurement with the AFM tip. The methods and apparatus
also include the ability to analyze light reflected/scattered from
the sample via a Raman spectrometer for complementary analysis by
Raman spectroscopy. Using a UV/vis source or IR source at higher
intensity it is possible to thermally desorb material from a sample
for analysis by mass spectrometry. The AFM tip can also be heated
to desorb material for mass spec analysis at even higher spatial
resolution.
Inventors: |
Shetty; Roshan; (Westlake
Village, CA) ; Kjoller; Kevin; (Santa Barbara,
CA) ; Prater; Craig; (Santa Barbara, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Anaysis Instruments Corp. |
Santa Barbara |
CA |
US |
|
|
Family ID: |
62241875 |
Appl. No.: |
15/826147 |
Filed: |
November 29, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62427671 |
Nov 29, 2016 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 21/1717 20130101;
G01Q 30/02 20130101; G01N 21/31 20130101; G01N 2021/1725 20130101;
G01N 21/65 20130101; G01Q 30/025 20130101; G01N 21/3563
20130101 |
International
Class: |
G01Q 30/02 20060101
G01Q030/02; G01N 21/3563 20060101 G01N021/3563; G01N 21/65 20060101
G01N021/65 |
Claims
1-21. (canceled)
22. An apparatus for rapidly characterizing a sample with infrared
radiation on a submicron scale, the apparatus comprising: a source
of infrared radiation configured to illuminate a sample with a beam
of infrared radiation to create an infrared illuminated area; a
source of ultraviolet-visible (UV-vis) radiation configured to
illuminate at least a region of the infrared illuminated area of
the sample with a beam of UV-vis light; a collector configured to
collect as collected light at least a portion of the UV-vis light
that is at least one of scattered, refracted, and reflected from
the sample; a receiver configured to analyze the collected light as
indicative of an infrared absorption of the region of the infrared
illuminated area; a scanner configured to create relative motion
between the sample and at least one of the beam of infrared light
and the beam of UV-vis light to measure the infrared absorption of
the sample over a scan area that includes a plurality of locations
on the sample; and an atomic force microscope subsystem configured
to measure a response of a cantilever probe over at least a portion
of the scan area.
23. The apparatus of claim 22, wherein the apparatus is configured
to use at least the infrared absorption at the plurality of
locations on the sample to construct a spatially resolved map of
infrared absorption of at least a portion of the sample.
24. The apparatus of claim 22, wherein the source of infrared
radiation illuminates the sample at plurality of wavelengths and
the receiver analyzes the collected light as indicative of an
infrared absorption spectrum for at least one location on the
sample.
25. The apparatus of claim 22, wherein the response of the
cantilever probe comprises a response to the beam of infrared
radiation.
26. An apparatus for rapidly characterizing a sample with infrared
radiation on a submicron scale, the apparatus comprising: a source
of infrared radiation configured to illuminate a sample with a beam
of infrared radiation to create an infrared illuminated area; a
source of ultraviolet-visible (UV-vis) radiation configured to
illuminate at least a region of the infrared illuminated area of
the sample with a beam of UV-vis light; a collector configured to
collect as collected light at least a portion of the UV-vis light
that is at least one of scattered, reflected and refracted from the
sample; a receiver configured to analyze the collected light as
indicative of an infrared absorption of the region of the infrared
illuminated area; and a Raman spectrometer configured to analyze
the collected light to analyze a Raman response of the sample.
27. The apparatus of claim 26, wherein the Raman response is used
to construct at least one Raman spectrum from at least one region
of the sample.
28. The apparatus of claim 26, wherein the receiver configured to
analyze the infrared absorption and the Raman response
substantially simultaneously.
29. The apparatus of claim 26, wherein the infrared absorption and
the Raman response are determined at a sub-micron resolution.
30. An apparatus for rapidly characterizing a sample with infrared
radiation on a submicron scale, the apparatus comprising: a source
of infrared radiation configured to illuminate a sample with a beam
of infrared radiation to create an infrared illuminated area; a
source of ultraviolet-visible (UV-vis) radiation configured to
illuminate at least a region of the infrared illuminated area of
the sample with a beam of UV-vis light; a collector configured to
collect as collected light at least a portion of the UV-vis light
that is at least one of scattered, reflected and refracted from the
sample; and a receiver configured for confocal optical microscopy
and further configured to analyze the collected light as indicative
of infrared absorption of the region of the infrared illuminated
area of the sample.
31. The apparatus of claim 30, wherein the receiver comprises at
least one of a confocal aperture and a pinhole.
32. An apparatus for rapidly characterizing a sample with infrared
radiation on a submicron scale, the apparatus comprising: a
broadband source of infrared radiation configured to illuminate a
sample with a beam of infrared radiation to create an infrared
illuminated area; a source of ultraviolet-visible (UV-vis)
radiation configured to illuminate at least a region of the
infrared illuminated area of the sample with a beam of UV-vis
light; a collector configured to collect as collected light at
least a portion of the UV-vis light that is at least one of
scattered, reflected and refracted from the sample; and a receiver
configured to analyze the collected light as indicative of infrared
absorption of the region.
33. The apparatus of claim 32, wherein the broadband source
comprises at least one of a globar and a thermal source.
34. The apparatus of claim 32, further comprising a modulator
configured to modulate the beam of infrared radiation.
35. The apparatus of claim 34, wherein the modulator is configured
to modulate the beam of infrared radiation at a frequency in excess
of 10 kHz.
36. An apparatus for rapidly characterizing a sample with infrared
radiation on a submicron scale, the apparatus comprising: a source
of infrared radiation configured to illuminate a sample with a beam
of infrared radiation to create an infrared illuminated area; a
source of ultraviolet-visible (UV-vis) radiation configured to
illuminate at least a region of the infrared illuminated area of
the sample with a beam of UV-vis light; a collector configured to
collect as collected light at least a portion of the UV-vis light
that is at least one of scattered, reflected and refracted from the
sample; and a receiver configured to analyze the collected light as
indicative of an infrared absorption of the sample; wherein the
receiver comprises at least one of a position sensitive detector
and an array detector; and wherein the infrared absorption of the
sample is measured with a spatial resolution of less than or equal
to 1 micrometer.
37. An apparatus for rapidly characterizing a sample with infrared
radiation on a submicron scale, the apparatus comprising: a source
of infrared radiation configured to illuminate a sample with a beam
of infrared radiation to create an infrared illuminated area; a
source of ultraviolet-visible (UV-vis) radiation configured to
illuminate at least a region of the infrared illuminated area of
the sample with a beam of UV-vis light; a collector configured to
collect as collected light at least a portion of the UV-vis light
that is at least one of scattered, reflected and refracted from the
sample; and a receiver configured to analyze the collected light as
indicative of an infrared absorption of the sample; wherein at
least one of the collector and the receiver includes a filter to
block at least a portion of the UV-vis light.
38. The apparatus of claim 37, wherein the filter comprises a
central obscuration.
39. An apparatus for rapidly characterizing a sample with infrared
radiation on a submicron scale, the apparatus comprising: a source
of infrared radiation configured to illuminate a sample with a beam
of infrared radiation; a first focusing optic configured to focus
the beam of infrared radiation to form an infrared illuminated
region of a sample; a source of ultraviolet-visible (UV-vis)
radiation configured to illuminate a sub-region of the sample with
a beam of UV-vis light; a second focusing optic configured to focus
the beam of UV-vis light at the sub-region of the sample, wherein
the sub-region at least partially overlaps the infrared illuminated
region; a collector configured to collect as collected light at
least a portion of the UV-vis light that is at least one of
scattered, reflected and refracted from interaction of the beam of
UV-vis light with the sample; a receiver configured to analyze the
collected light and provide an indication of an infrared absorption
of the sub-region.
40. The apparatus of claim 39, wherein the first focusing optic has
a numerical aperture of at least 0.7.
41. The apparatus of claim 39, wherein the second focusing optic
comprises a parabolic mirror.
42. The apparatus of claim 39, wherein the beam of UV-vis light
illuminates a sub-region of the sample that is smaller than the
infrared illuminated area.
43. The apparatus of claim 39, wherein the collector comprises an
objective that is further configured to focus at least one of the
beam of infrared radiation and the beam of UV-vis light on the
sample.
44. The apparatus of claim 39, wherein the collector comprises an
objective, and wherein the source of UV-vis radiation and the
objective are arranged such that the beam of UV-vis light is
focused on the sample by the objective and the collected UV-vis
light is collected by the objective.
45. A method for rapidly characterizing a sample with infrared
radiation on a submicron scale, the method comprising: illuminating
a sample with a beam of infrared radiation to create an infrared
illuminated area; illuminating at least a region of the infrared
illuminated area of the sample with a beam of ultraviolet-visible
(UV-vis) light; collecting as collected light at least a portion of
the UV-vis light that is at least one of scattered, refracted, and
reflected from the sample; analyzing the collected light to
determine an infrared absorption of the region of the infrared
illuminated area; creating relative motion between the sample and
at least one of the beam of infrared light and the beam of UV-vis
light to measure the infrared absorption of the sample over a scan
area that includes a plurality of locations on the sample; and
measuring a response of a cantilever probe over at least a portion
of the scan area with an atomic force microscope.
46. The method of claim 45, further comprising constructing a
spatially resolved map of infrared absorption of at least a portion
of the sample using at least the infrared absorption at the
plurality of locations on the sample.
47. The method of claim 45, wherein: illuminating the sample with a
beam of infrared radiation includes illuminating the sample at
plurality of wavelengths; and analyzing the collected light
includes analyzing the collected light as indicative of an infrared
absorption spectrum for at least one location on the sample.
48. The method of claim 45, wherein the response of the cantilever
probe comprises a response to the beam of infrared radiation.
49. A method for rapidly characterizing a sample with infrared
radiation on a submicron scale, the method comprising: illuminating
a sample with a beam of infrared radiation to create an infrared
illuminated area; illuminating at least a region of the infrared
illuminated area of the sample with a beam of ultraviolet-visible
(UV-vis); collecting as collected light at least a portion of the
UV-vis light that is at least one of scattered, refracted, and
reflected from the sample; analyzing the collected light to
determine an infrared absorption of the region of the infrared
illuminated area; and analyzing the collected light to detect a
Raman response of the sample.
50. The method of claim 49, further comprising constructing at
least one Raman spectrum from the Raman response.
51. The method of claim 49, further comprising analyzing the
infrared absorption and the Raman response substantially
simultaneously.
52. The apparatus of claim 49, wherein the infrared absorption and
the Raman response are determined at a sub-micron resolution.
53. A method for rapidly characterizing a sample with infrared
radiation on a submicron scale, the method comprising: illuminating
a sample with a beam of infrared radiation to create an infrared
illuminated area; illuminating at least a region of the infrared
illuminated area of the sample with a beam of ultraviolet-visible
(UV-vis) light; collecting as collected light at least a portion of
the UV-vis light that is at least one of scattered, refracted, and
reflected from the sample; analyzing the collected light at a
receiver configured for confocal optical microscopy, wherein
analyzing the collected light includes determining an infrared
absorption of the region of the infrared illuminated area.
54. The method of claim 53, wherein the receiver comprises at least
one of a confocal aperture and a pinhole.
55. A method for rapidly characterizing a sample with infrared
radiation on a submicron scale, the method comprising: illuminating
a sample with a beam of infrared radiation from a broadband source
of infrared radiation to create an infrared illuminated area;
illuminating at least a region of the infrared illuminated area of
the sample with a beam of ultraviolet-visible (UV-vis) light;
collecting as collected light at least a portion of the UV-vis
light that is at least one of scattered, refracted, and reflected
from the sample; analyzing the collected light to determine an
infrared absorption of the region of the infrared illuminated area;
and analyzing the collected light to detect a Raman response of the
sample.
56. The method of claim 55, wherein the broadband source of
infrared radiation comprises at least one of a globar and a thermal
source.
57. The method of claim 55, further comprising modulating the beam
of infrared radiation at a modulator.
58. The method of claim 57, wherein the modulator is configured to
modulate the beam of infrared radiation at a frequency in excess of
10 kHz.
59. A method for rapidly characterizing a sample with infrared
radiation on a submicron scale, the method comprising: illuminating
a sample with a beam of infrared radiation from a source of
infrared radiation to create an infrared illuminated area;
illuminating at least a region of the infrared illuminated area of
the sample with a beam of ultraviolet-visible (UV-vis) light;
collecting as collected light at least a portion of the UV-vis
light that is at least one of scattered, refracted, and reflected
from the sample; and analyzing the collected light at a receiver
having a position sensitive detector and an array detector to
determine an infrared absorption of the region of the infrared
illuminated area, wherein the infrared absorption of the infrared
illuminated area is measured with a spatial resolution of less than
or equal to 1 micrometer.
60. A method for rapidly characterizing a sample with infrared
radiation on a submicron scale, the method comprising: illuminating
a sample with a beam of infrared radiation to create an infrared
illuminated area; illuminating at least a region of the infrared
illuminated area of the sample with a beam of ultraviolet-visible
(UV-vis) light; collecting as collected light at least a portion of
the UV-vis light that is at least one of scattered, refracted, and
reflected from the sample; analyzing the collected light at a
receiver to determine an infrared absorption of the region of the
infrared illuminated area; and blocking at least a portion of the
UV-vis light with a filter arranged at at least one of the
collector and the receiver.
61. The method of claim 60, wherein the filter comprises a central
obscuration.
62. A method for rapidly characterizing a sample with infrared
radiation on a submicron scale, the method comprising: illuminating
a sample with a beam of infrared radiation; focusing the beam of
infrared radiation at an infrared illuminated region of the sample
with a first focusing optic; illuminating at least a region of the
infrared illuminated area of the sample with a beam of
ultraviolet-visible (UV-vis) light; focusing the beam of UV-vis
light at a sub-region of the sample that partially overlaps the
infrared illuminated region with a second focusing optic;
collecting as collected light at least a portion of the UV-vis
light that is at least one of scattered, refracted, and reflected
from the sample; and analyzing the collected light to determine an
infrared absorption of the region of the infrared illuminated
area.
63. The method of claim 62, wherein the first focusing optic has a
numerical aperture of at least 0.7.
64. The method of claim 62, wherein the second focusing optic
comprises a parabolic mirror.
Description
RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Application No. 62/427,671 filed Nov. 29, 2016, which
is hereby incorporated herein in its entirety by reference.
[0002] AFM-IR may be a useful technique for measuring and mapping
optical properties/material composition of some surfaces with
resolution approaching nanometer scale. Various aspects of the
technique are described in U.S. Pat. Nos. 8,869,602, 8,680,457,
8,402,819, 8,001,830, 9,134,341, 8,646,319, 8,242,448, and U.S.
patent application Ser. No. 13/135,956, by common inventors and
commonly owned with this application. These applications are
incorporated by reference in their entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Aspects and advantages of the embodiments provided herein
are described with reference to the following detailed description
in conjunction with the accompanying drawings.
[0004] Throughout the drawings, reference numbers may be re-used to
indicate correspondence between referenced elements. The drawings
are provided to illustrate example embodiments described herein and
are not intended to limit the scope of the disclosure.
[0005] FIG. 1 shows a simplified schematic diagram of an
illustrative embodiment.
[0006] FIG. 2 shows shuttling of IR beam between AFM and
photothermal.
[0007] FIG. 3 shows shuttling between IR and Raman
[0008] FIG. 4 illustrates using same objective for AFM as for
UV/vis light collection.
[0009] FIG. 5 illustrates an embodiment including laser scanning
confocal microscopy and spectroscopy.
[0010] FIG. 6 shows an embodiment related to that shown in FIG. 2
in which the IR and UV/vis light are focused with the same
objective lens.
[0011] FIG. 7 shows an embodiment where the IR source is a
broadband source.
[0012] FIG. 8 shows an embodiment including mass spectrometry.
[0013] FIG. 9 shows an embodiment employing total internal
reflection illumination of the infrared radiation.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Definitions
[0014] Interacting a probe with a sample" refers to bringing the
probe tip close enough to the surface of a sample such that one or
more near field interactions occur, for example the attractive
and/or repulsive tip-sample forces, and/or the generation and/or
amplification of radiation scattered from an area of the sample in
proximity of the probe apex. The interaction can be contact mode,
intermittent contact/tapping mode, non-contact mode, pulsed force
mode, and/or any lateral modulation mode. The interaction can be
constant or as in preferred embodiments, periodic. The periodic
interaction may be sinusoidal or any arbitrary periodic waveform.
Pulsed force modes and/or fast force curve techniques may also be
used to periodically bring the probe to a desired level of
interaction with a sample, followed by a hold period, and then a
subsequent probe retraction.
[0015] "Illuminating" means to direct radiation at an object, for
example a surface of a sample, the probe tip, and/or the region of
probe-sample interaction. Illumination may preferably include
radiation in the infrared wavelength range, but other wavelengths
may also be used. Illumination may include any arbitrary
configuration of radiation sources, pulse generators, modulator,
reflecting elements, focusing elements and any other beam steering
or conditioning elements.
[0016] "Infrared source" and "source of infrared radiation" refer
to one or more optical sources that generates or emits radiation in
the infrared wavelength range, generally between 2-25 microns. The
radiation source may be one of a large number of sources, including
thermal or Globar sources, supercontinuum laser sources, frequency
combs, difference frequency generators, sum frequency generators,
harmonic generators, optical parametric oscillators (OPOs), optical
parametric generators (OPGs), quantum cascade lasers (QCLs),
nanosecond, picosecond, femtosecond and attosecond laser systems,
CO2 lasers, heated cantilever probes or other microscopic heaters,
and/or any other source that produces a beam of radiation. The
source emits infrared radiation in a preferred embodiment, but it
can instead or also emit in other wavelength ranges, for example
from ultraviolet to THz. The source may be narrowband, for example
with a spectral width of <10 cm.sup.-1 or <1 cm.sup.-1 less,
or may be broadband, for example with a spectral width of >10
cm.sup.-1, >100 cm.sup.-1 or greater than 500 cm.sup.-1.
[0017] "UV/vis source" refers to a source of ultraviolet (UV)
and/or visible light radiation. The UV/vis source may comprise a
gas laser, a laser diode, a superluminescent diode (SLD), a UV
and/or visible laser beam generated via sum frequency or difference
frequency generation, for example. It may also comprise any or
other sources of UV and/or visible light that can be focused to a
spot on the scale smaller than 2.5 micrometer, and preferably
smaller than 1 micrometer.
[0018] "Spectrum" refers to a measurement of one or more properties
of a sample as a function of wavelength or equivalently (and more
commonly) as a function of wavenumber.
[0019] "Optical property" refers to an optical property of a
sample, including but not limited to index of refraction,
absorption coefficient, reflectivity, absorptivity, real and/or
imaginary components of the index refraction, real and/or imaginary
components of the sample dielectric function and/or any property
that is mathematically derivable from one or more of these optical
properties.
[0020] "Optical response" refers to the result of interaction of
radiation with a sample. The optical response is related to one or
more optical properties defined above. The optical response can be
an absorption of radiation, a temperature increase, a thermal
expansion, a photo-induced force, the reflection and/or scattering
of light or other response of a material due to the interaction
with radiation.
[0021] "Signal indicative of" refers to a signal that is
mathematically related to a property of interest. The signal may be
an analog signal, a digital signal, and/or one or more numbers
stored in a computer or other digital electronics." The signal may
be a voltage, a current, or any other signal that may be readily
transduced and recorded. The signal may be mathematically identical
to the property being measured, for example explicitly an absolute
phase signal or an absorption coefficient. It may also be a signal
that is mathematically related to one or more properties of
interest, for example including linear or other scaling, offsets,
inversion, or even complex mathematical manipulations.
[0022] A "scanning probe microscope (SPM)" refers to a microscope
where a sharp probe is interacted with a sample surface and then
scanned the surface while measuring one or more properties of the
sample surface. The scanning probe microscope may be an Atomic
Force Microscope (AFM) which may include cantilever probe with a
sharp tip. The SPM generally include a capability for measuring the
motion, position and or other response of the probe tip and/or an
object to which the probe tip is attached, e.g. a cantilever or a
tuning fork or MEMS device, for example. The most common method
includes using an optical lever system where a laser beam is
bounced off the cantilever probe to measure deflection of the
cantilever. Alternatives include self-sensing techniques like
piezoresistive cantilevers, tuning forks, capacitive sensing and
other techniques. Other detection systems may measure other
properties such as force, force gradient, resonant frequency,
temperature and/or other interactions with the surface or responses
to the surface interaction.
[0023] Cantilever probes" are generally microfabricated cantilevers
made from silicon, silicon nitride or other semiconductor based
materials. Probes have also been fabricated from metals and
polymeric materials. In general the probe only needs to have a
sharp tip that can interact with the sample and support for some
mechanism to detect the interaction, e.g. by the bending of the
cantilever probe, or the change in resistance, resonance frequency
or other property that is indicative of the interaction between the
probe time and the sample.
[0024] A "scanner" is one or more scanning mechanisms used to
generate relative translation between the probe and the sample so
that the probe can interact with and measure properties of a
plurality of positions on a sample. The scanning mechanism can move
either the probe, the sample or a combination thereof. The scanning
mechanisms are usually piezoelectric devices, but can also employ
other mechanisms like electromagnetic, electrostatic,
electrostrictive and other drive mechanisms that induce a desired
motion in response to a given control signal or command. Scanners
include, but are not limited to piezoelectric tubes, piezoelectric
stacks, piezoelectric driven flexure stages, voice coils, and other
mechanisms for providing precision translation.
[0025] An "SPM controller" refers to a system to facilitate data
acquisition and control of the AFM-IR system. The controller may be
a single integrated electronic enclosure or may comprise multiple
distributed elements. The control elements may provide control for
positioning and/or scanning of the probe tip and/or sample. They
may also collect data about the probe deflection, motion or other
response, provide control over the radiation source power,
polarization, steering, focus and/or other functions. The control
elements etc. may include a computer program method or a digital
logic method and may be implemented using any combination of a
variety of computing devices (computers, Personal Electronic
Devices), analog and/or digital discrete circuit components
(transistors, resistors, capacitors, inductors, diodes, etc.),
programmable logic, microprocessors, microcontrollers,
application-specific integrated circuits, or other circuit
elements. A memory configured to store computer programs and may be
implemented along with discrete circuit components to carry out one
or more of the processes described herein.
[0026] A "lock-in amplifier" is a device and/or an algorithm that
demodulates the response of a system at one of more reference
frequencies. Lock-in amplifiers may be electronic assemblies that
comprise analog electronics, digital electronics, and combinations
of the two. They may also be computational algorithms implemented
on digital electronic devices like microprocessors, field
programmable gate arrays (FPGAs), digital signal processors, and
personal computers. A lock-in amplifier can produce signals
indicative of various metrics of an oscillatory system, including
amplitude, phase, in phase (X) and quadrature (Y) components or any
combination of the above. The lock-in amplifier in this context can
also produce such measurements at both the reference frequencies,
higher harmonics of the reference frequencies, and/or sideband
frequencies of the reference frequencies.
[0027] "Photothermal distortion" refers to a change in the
properties of a sample due to absorption of optical energy, for
example the absorption of IR radiation. The photothermal distortion
may refer to a change in index of refraction, reflectivity, thermal
expansion, surface distortion, or other effects that can be
detected with the tip of an atomic force microscope and/or a beam
of UV/visible radiation.
[0028] Photothermal Imaging and Spectroscopy
[0029] FIG. 1 shows an embodiment of system for rapid photothermal
infrared imaging and spectroscopy with sub-diffraction limited
spatial resolution. A beam of infrared radiation 100 is directed
from an infrared source 102 at a region 104 of a sample 106. The
infrared source may be a tunable narrowband source, e.g. an
infrared laser or a broadband source. If the beam 100 contains one
or more wavelengths that are absorbed by material components in the
illuminated region of the sample, the absorbed radiation will cause
heating of the absorbing components. This absorbed heat can be
detected in one of two ways. First, it can be detected with a
focused beam of ultraviolet or visible (UV/vis) radiation. A source
of UV/vis radiation 108 can be optionally collimated using one or
more lenses 110 and then directed through a polarizing beamsplitter
112 to a quarter wave plate 114 and then focused by an objective
116 onto a portion of the region of the sample illuminated by the
infrared radiation beam 100. The heating of absorbing regions of
the sample can cause light reflected or more generally scattered
from the sample surface to deviate from its normal trajectory
without the sample being illuminated with infrared light. For
example, the sample may deform due to thermal expansion causing
changes in the reflection and/or refraction from the sample.
Additionally, the sample or the surrounding medium can heat and
change the local index of refraction of the sample. The resulting
"thermal lensing" can alter the beam path of UV/vis light
scattered, refracted or reflected from the sample. Light returning
from the sample can be collected by objective 116 (or alternately
an additional objective lens placed below the sample, not shown),
and then sent to a receiver 120. In the case of collecting the
light via the illuminating objective 116, the collected light can
pass through the quarter waveplate 114 such that the polarization
is rotated 90 degrees relative to the incident beam. Then
polarizing beamsplitter 112 will direct the polarization rotated
beam towards a receiver 120 that can comprise a detector 121 or
spectrometer 122 or both. Optionally a portion of the beam 118 from
the polarizing beam splitter may be blocked by filter 119. Filter
119 may have a central obstruction, for example to block the
majority of undeflected central rays, thus increasing the dynamic
range of the detector 121 and/or spectrometer 122. That is, the
detector can be operated at higher gain and/or longer integration
times before saturating if the central part of the undeviated beam
is blocked. Alternately there can be an additional lens in the
collection arm that focuses beam 118 to a spot either at or before
the detector 121. In the case that the additional lens focuses the
beam to a post before the detector, a pinhole may be placed at the
focused spot to block light that is scattered or reflected from
regions outside the sample focal plane. Detector 121 may be a
detector that measures the relative intensity of the beam incident
on it, for example a conventional photodiode, an avalanche
photodiode, photomultiplier tube, and/or other detector that
produces a signal that a signal indicative of an intensity of the
light incident on the detector. Alternately, the detector 121 can
be a position sensitive detector, for example a linear photodiode,
a dual or quad segment detector or a multi-detector array. In this
case, the detector can also be sensitive to positional shifts in
the reflected/scattered beam, for example due to angular deviations
in the beam and/or lateral shifts. Alternately detector 121 may
comprise a phase sensitive detector, comprising further an
interferometric detection scheme that produces a signal indicative
of the optical phase or optical phase shift of the beam incident on
the detector. In these embodiments the system can measure the
change in intensity, beam angle and/or optical retardation induced
by a temperature change in the sample due to the interaction or
absorption of infrared light by the sample.
[0030] The infrared light source can be pulsed or modulated. For
example controller 123 may generated trigger or sync pulses that
command the light source to pulse at a specified rate. Alternately,
the light source may pulse based on internal timing and send a sync
pulse back to controller 123. Alternately, the light source may
have an external modulator 101 that periodically modulates its
intensity. In a preferred embodiment the light source is modulated
or pulsed at frequencies in excess of 10 kHz, 100 kHz, or 1 MHz.
Modulating the infrared light at high frequencies reduces the
effective thermal diffusion length which could otherwise compromise
the spatial resolution of this technique. The detected UV/vis light
is then analyzed by controller 123 and/or external signal
conditioning/demodulating electronics. In one embodiment the
detector signal is analyzed by a lock-in amplifier or equivalent
device to measure an amplitude of the UV/vis modulation at the
modulation frequency of the laser light source or a harmonic
frequency thereof. By using phase sensitive detection such as a
lock-in amplifier it is possible to measure only the impact of the
infrared light that is absorbed by the sample and causes a periodic
deviation of the UV/vis beam resulting from the sample heating. By
measuring the amplitude of the UV/vis modulation at plurality of
locations on the sample 106, it is possible to make an image 128 of
the infrared response of the sample. A key aspect of this
arrangement is that the infrared properties of the sample can be
measured on a scale below the diffraction limit of the infrared
light source that illuminates the sample. Instead, the spatial
resolution is limited only by the spatial resolution limit of the
illuminating UV/vis light beam. This spatial resolution can be as
low as .lamda./2, where .lamda. is the wavelength of the UV/vis
light beam. The UV/vis modulation can also be measured as a
function of the wavelength of the infrared source 102 to create a
spectrum 136 of the IR absorption, reflection and/or transmission
of the sample. In the case of a narrowband source, e.g. a source
with a spectral linewidth of typically <10 cm.sup.-1 and
preferably <1 cm.sup.-1 it is possible to create a spectrum
directly by measuring the UV/vis modulation as a function of the
emission wavelength (or equivalently wavenumber) of the infrared
source. In the case of a broadband source (typical linewidth
>100 cm.sup.-1), it may be desirable to use Fourier transform
techniques to extract the wavelength dependence of the UV/vis
modulation and thus extract spectrum 136. In this case the light
from IR source 102 is passed through an interferometer comprising a
beamsplitter, a fixed mirror and a moving mirror, before the light
is incident on the sample. The moving mirror in the interferometer
can be scanned over a range of different positions while monitoring
the UV/vis modulation to create an interferogram. The interferogram
can then be Fourier transformed to obtain a spectrum.
[0031] The spatially resolved map 128 can be created in two main
ways. First, the focused IR and uv/VIS light spots can be held
stationary and the sample 106 can be scanned relative to these
focused spots, for example with sample scanner 130. Alternately,
the UV/vis light beam may be scanned across the sample, for example
using galvo scanning mirrors as employed in laser scanning confocal
microscopy. Note that it is possible for the IR light beam 100 to
be either stationary or scanned depending on the power requirements
and the focused spot size. In one embodiment the IR beam 100 is
synchronously scanned with the UV/vis spot such that the peak
intensity of the IR beam and the center of the UV/vis spot are
substantially overlapped. Alternately, the IR beam can be
configured to be large enough such that it covers the range of
travel of the scanned UV/vis beam. In one embodiment the IR source
can be a thermal source, for example a globar as conventionally
used in Fourier Transform Infrared (FTIR) spectroscopy and
microscopy. Alternately small area thermal emitters for example
from Axetris or NovaIR or other vendors can be employed. In the
case of a thermal emitter it is desirable to modulate the
temperature of the device or the output IR power. Some commercial
small area thermal emitters can be modulated up to the 100 Hz
regime. AFM cantilevers with integral resistive heaters can be
modulated in the kHz range due to their small active area and small
thermal time constant. Susuma Noda and colleagues at the University
of Kyoto have fabricated thermal emitters that can be modulated at
frequencies in the range of 10 kHz (doi:10.1038/nmat4043). Various
external modulators can also be employed, for example photoelastic
modulators, high speed choppers (for example from Scitec up to 100
kHz), MEMS mirrors, piezoelectrically deformed mirrors and other
modulators that can adjust the intensity, angle, and/or focused
spot size of an infrared beam.
[0032] A desirable aspect of the device of FIG. 1 is that it can be
used to perform both infrared photothermal optical microscopy and
scanning probe microscopy measurements on the same platform. This
can be achieved without having to manually move the sample from one
instrument to another and thus can support collocated, sequential,
and even in some cases simultaneous measurements.
[0033] In one embodiment the UV/vis source may comprise a
superluminescent diode (SLD). SLDs can be advantageous in this
apparatus as they have relatively short coherence lengths.
Conventional lasers and laser diodes can have coherences lengths in
the meter and millimeter range. This can cause a problem as a light
source for optical photothermal measurements since scattered light
and multiply reflected light can self-interfere causing unwanted
parasitic oscillations in the measurement in the absorption of IR
light with the UV-vis beam. For this reason in one embodiment a
superluminescent diode is chosen as the UV-vis source. For example
Exalos makes superluminescent diodes with spatial coherence in the
range of 4-30 .mu.m. These short coherence lengths mean that
multiple reflections that occur from surfaces or scatterers roughly
more than the coherence length away in distance will not strongly
self interfere, thus resulting in optical photothermal images with
fewer interference artifacts. Qphotonics sells a 405 nm
superluminescent diode coupled to a single mode fiber with a 3.6 um
mode diameter. Using a high NA and low aberration objective along
with an appropriate tube lens it is possible to focus light from
the single mode fiber to a near diffraction limited spot, thus
achieving high spatial resolution but without the optical
interference issues associated with a narrowband source.
[0034] In one embodiment the image 128 created by using the UV/vis
beam to read out IR absorption can also be used as a "survey scan"
for a higher resolution measurement performed by atomic force
microscope based infrared spectroscopy (AFM-IR) or
scattering-scanning nearfield optical microscopy (s-SNOM) or
tip-enhanced Raman spectroscopy (TERS) or any other probe-based
microscope scan, or for laser based mass spectrometry, as described
later. In the AFM-IR technique the sample 106 is also illuminated
by a beam 100 of infrared radiation from an IR source 102. In this
case if a portion of the illuminated region absorbs infrared light,
the absorbing region can heat up and undergo thermal expansion,
creating a force impulse on a probe tip 130 of the AFM. Alternately
IR radiation interacting with the sample may induce a force between
the tip and sample due to induced electric field interactions. In
either case the force on the probe tip can cause a bending of the
probe that can be detected optically or by other means. In one
embodiment it is possible to employ the same UV/vis laser system
used to read out the IR absorption as described above. In this case
the laser scanning mechanism (e.g. galvos) can be used to move the
UV/vis laser beam from a region on the sample to the back of the
cantilever. In one embodiment the cantilever tilt angle and the
numerical aperture of the objective lens 116 are selected such that
the light reflected off the AFM cantilever is reflected at an angle
outside the collection angle of the objective 116. For example a
Mitutoyo 20.times. 0.42 NA long working distance objective can be
used to both focus the UV/vis laser spot on the cantilever or
sample while still providing sufficient clearance for the AFM
deflection measurement outside
[0035] the collection angle of the lens. The 20.times. 0.42 NA
objective has a half angle of roughly 25.degree.. So if the
cantilever is tilted at 25 degrees or more, the beam 124 reflected
from the cantilever will pass outside the collection angle of
objective 116 and can be collected by position sensitive detector
126. Despite this long working distance, the 20.times. 0.42 NA
objective can still focus the UV/vis beam to a spot smaller than 1
micron in diameter with light sources 108 up to around 670 nm
wavelength and with an M2 beam quality of 1.2 or better. Similarly
a 10.times. 0.24 NA 38 mm working distance objective can be used.
This objective can also achieve focused spot diameter just below 1
um with 408 nm wavelength or shorter source. It has the advantage
of a smaller collection angle of 14 degrees which requires a
cantilever tilt of only 7 degrees or more to have the reflected
beam outside the collection angle of the optics.
[0036] With a combined system that include UV/vis and AFM-IR
mapping of the IR absorption it is possible to have both rapid
large area mapping and extremely high spatial resolution IR
mapping. For example a large region can be scanned rapidly using
the UV/vis beam to acquire a survey scan 128 with spatial
resolution on scale from 0.2-1 .mu.m. Then a smaller region of
interest 132 can be identified in the survey scan 128. The smaller
region 132 can then be measured by AFM-IR to obtain a high
resolution image 134 with a spatial resolution down to the
nanometer scale.
[0037] Advantageously the receiver 120 that collects the radiation
reflected/scattered from the sample surface may be a detector 121
or a spectrometer 122 or a combination thereof. In one embodiment
the spectrometer 122 comprises a Raman spectrometer. Because the
sample illuminating beam is preferably in the UV or visible
wavelengths (or alternately shortwave IR, e.g. 1064 nm), it can
also be used to excite Raman response in the sample. In this case
the back scattered/reflected light can be analyzed by a Raman
spectrometer for Raman shifted photons. In this way it is possible
for the same instrument to collect both infrared and Raman spectra
of the same sample and with sub-micron spatial resolution for both
measurements.
[0038] FIG. 2 illustrates an optical arrangement under one
embodiment that supports both optical photothermal and AFM-based
measurements using the same objective lens. FIG. 2A shows one
arrangement for optical photothermal measurements. UV/vis light 200
passes through objective 202 where it is focused 204 onto a region
206 of sample 208. Scattered and/or reflected light is passed back
up through the objective and detected and analyzed per the methods
described in the text associated with FIG. 1. FIG. 2B shows an
arrangement for AFM based measurements. In this case a light beam
210 is directed off the center of the optical axis of objective
202. For example the beam 210 may be position near the outside
diameter of the input aperture of the objective 202. When the beam
212 exits the objective 202 it is directed to strike prove 214, for
example an AFM cantilever probe. Reflected beam 216 is directed on
an alternate optical path than the incoming beams 210/212 and exit
the objective on a parallel but offset path 218. The offset thus
makes it possible to easily separate the incoming and outgoing
beams and direct outgoing beam 218, for example using mirror 220 to
direct the reflected beam to a position sensitive detector 220 for
measuring the deflection of probe 214.
[0039] FIG. 3 shows an embodiment of the apparatus comprising top
side, side-angle illumination of the sample with an IR beam and a
high resolving power UV/vis readout. In this embodiment an IR light
beam 308 is illuminates sample 306 with a low angle of
illumination. The IR light beam 308 is focused to a spot on sample
306 using a focusing element 312 that can comprise one or more
lenses and/or curved mirrors. In one embodiment the focusing
element 312 can be a parabolic mirror, for example an off axis
parabolic mirror. UV/visible light beam 300 is directed through
objective 302 to focus light 304 on a region of sample 306. The
cone angle 310 of the IR beam 308 can be chosen such that it can
fit under the working distance and angular clearance of object 302.
For example objective 302 can be a 100.times. 0.7 NA objective from
Mitutoyo with a 6 mm working distance. This working distance and
the objective's housing provide support for an IR illumination cone
angle of at roughly 32 degrees, corresponding to an illumination NA
of 0.28 and a 16 degree angle of incidence. This illumination NA
can be more than sufficient to focus the IR radiation 308 to a
small enough spot to obtain the intensity at the sample required
for optical photothermal detection. To achieve high spatial
resolution, only the UV/vis beam needs to be tightly focused. The
IR beam may be focused to a much larger spot, as long as the
focused spot has sufficient intensity to generate a detectable
deflection in the visible beam. Smaller IR illumination angles can
also be used, for example to provide more clearance between the IR
beam 308 (and focusing element 312) and the sample 306.
[0040] In cases where it is desired to use higher NA focusing
optics for the UV/vis beam it is possible to achieve side angle
illumination using a specially modified objective. FIG. 4 shows an
embodiment involving a high NA objective 400 and side angle
illumination with IR beam 406. In this case the short working
distance of standard high NA objectives may not provide adequate
clearance for side angle illumination. For example objectives with
NA of 0.85 or higher may have working distances of much less than 1
mm. In the case of extremely high NA UV/visible light objective, it
is possible to create an illumination path for the IR light by
creating a custom objective with a hole or other clearance for side
illumination. For example it is possible to machine both the
objective housing and if desired a small portion of the edge of the
final objective lens. FIG. 4 shows a high NA objective 400 with a
UV/vis beam 402 focused on sample 404. A portion 406 of objective
400 is cut away to provide access for side angle illumination by IR
beam 408.
[0041] FIG. 5 shows an embodiment combining photothermal IR
spectroscopy and laser scanning confocal microscopy/spectroscopy.
An IR source 502 focuses a beam of IR radiation 504 onto sample
506. The sample can be scanned under the beam via scanner 508.
Scanner 508 may be a piezo driven stage, a mechanical translation
stage or a combination thereof, which can be a mechanical
translation. The sample can also be measured by AFM probe 510 to
measure both the topography and photothermal response of the
sample. The sample 506 is also illuminated by a beam of UV,
visible, or near IR light via light source 512. Light from light
source 512 is collimated by lens 514 and then directed to
beamsplitter or dichroic 516. A portion of the light is optionally
directed towards scan mirrors 518, typically a pair of galvo-based
steering mirrors. Light reflected off the galvo scan mirrors can be
focused by scan lens 520 to produce an intermediate focus at 522.
Tube lens 524 in combination with objective 530 transfer an image
of the intermediate focus 522 to a position on sample 506. As the
galvo scan mirrors 518 move, the position of the focused spot on
the sample can translate across the sample. If the focus spot of
beam 504 is large relative to the scan range provided by the scan
mirrors 518, the IR focused spot can remain stationary and the scan
mirrors 518 can rapidly map the photothermal response of the
sample. Light reflected and/or scattered from the sample 506 is
recaptured by objective 530 and retraces the incident light path.
An optional beamsplitter/dichroic or removable mirror 526 can be
used to provide an auxiliary optical access for white light
illumination and/or a camera view of the sample. Light that passes
through or by beamsplitter/mirror 526 continues along the incident
light path back to beamsplitter/dichroic 516. In this case we
consider now the light that passes through the
beamsplitter/dichroic 516 which then goes to an optional focus lens
530 which focuses the light to a spot on a confocal aperture or
pinhole. This pinhole allows light to pass through that is confocal
with the sample focal plane and blocks out of focus light. The
aperture at this location may be an adjustable aperture, or have
multiple selectable pinholes of various sizes to allow for
appropriate tradeoffs between signal and depth of focus. Light
passing through the pinhole 532 can be coupled to a fiber 534 or go
directly to a detector/spectrometer assembly 535. The
detector/spectrometer 535 may include a
mirror/dichroic/beamsplitter 536 to divide or direct the collected
light along paths to either or both of a UV/visible light detector
540 or spectrometer 538. For example 536 can be a rotatable or
flipper mirror to direct the light to either a detector 540 or a
spectrometer 538 or 536 can be a beam splitter to divide the light
between the two paths. In one embodiment, spectrometer 538 is a
Raman spectrometer, thus allowing the system to perform
complementary measurements of both IR spectroscopy and Raman
spectroscopy on the same sample and even at the same time if
desired. In the case of using a spectrometer it is possible that
beamsplitter 536 is a dichroic that reflects or transmits the
excitation wavelength while doing the opposite for Raman shifted
light. In this way the light can be divided by wavelength and
separately analyzed to make photothermal IR absorption measurements
at the excitation wavelength of source 512 and Raman spectroscopic
measurements with wavelength shifted light at spectrometer 538.
[0042] FIG. 6 shows an embodiment related to that shown in FIG. 2
in which the IR and UV/vis light are focused with the same
objective lens. IR light source 600 emits a beam 601 of IR
radiation towards optional mirror 602 which reflects the beam
towards objective 604 where it is focused 606 to a spot on sample
608. Objective 606 is preferably a reflective objective, for
example a Cassegrain/Schwarzschild objective such that it can focus
both UV/Vis and IR light at the same point in space. Objective 606
may also be a refractive objective, for example with lenses made of
an IR transparent material, for example ZnSe. IR light absorbed by
sample 608 causes a temperature increase in the sample resulting in
a photothermal distortion in the sample, for example a change in
index of refraction, change in reflectivity and/or change in
surface deformation. UV/vis light source 624 is collimated by lens
626 and reflected by dichroic mirror or beamsplitter 628 through
the same objective 604 and is focused onto substantially the same
region of the sample where the IR light beam is focused.
Temperature increases in the sample and resulting photothermal
distortions of the sample can cause a change in the intensity,
angle and/or optical phase of the reflected/scattered visible light
from source 626. The scattered/reflected UV/vis light is collected
by objective 604 and passed up to dichroic mirror/beamsplitter 614
where it is directed to receiver 618. Receiver 618 can comprise a
UV/vis detector 620 and/or a spectrometer 622, as described
previously with respect to FIGS. 1 and 5. The sample 608 can be
scanned under the focused UV/vis and IR spots with scanner 610 to
provide a map of the IR absorption of the sample. The wavelength of
IR source 600 can be swept to obtain spectroscopic measurements of
the sample 608. The scanner 610 can comprise a large travel (mm to
cm scale) mechanical stage for coarse imaging and a piezo stage for
fine imaging either by the UV/vis photothermal measurement or using
AFM probe 612 to read out forces on the AFM probe induced by the IR
radiation incident on the samples.
[0043] FIG. 7 shows an embodiment where the IR source is a
broadband source, for example a globar or other thermal source.
Broadband IR source 700 emits a beam of radiation 702 comprising a
plurality of wavelengths, preferably comprising a broad range of
wavelengths for example 2.5.sup.-10 microns or more in wavelength
range. The broadband IR beam 702 is directed towards beamsplitter
704 where the beam is divided into two paths. On one path the
broadband IR light strikes fixed mirror 708 and on the other path
it strikes moving mirror 706. The two beams recombine with a
relative phase shift determined by the position of moving mirror
706. The combined beams are then directed through or onto optional
modulator 710 that modulates the intensity and/or angle of the IR
beam. The modulated beam is reflected off optional mirror 712 and
directed through objective 714 where it is focused 716 on a sample
718. IR light that is absorbed by the sample creates a photothermal
distortion that is read out by either an AFM probe 722 or a
UV/visible light beam as discussed previously. In the case of read
out by the AFM probe, the modulation frequency of modulator 710 can
be set to substantially correspond with a resonance frequency of
probe 722. In this configuration, the detection of the photothermal
deflection of the AFM cantilever is amplified by the quality factor
of the cantilever resonance. This resonant amplification allows the
use of a thermal source (i.e. globar) which has much lower cost and
much lower brilliance than an IR laser. The modulator 710 can also
be used to create a modulation in the excitation that can then be
used for lock-in detection of the UV-vis light intensity. The
modulator frequency can also be set to correspond to a resonant
frequency of a resonant amplifier, for example as described by
United States Patent Application 20140361150.
[0044] The current apparatus can also be combined with mass
spectrometry as shown in FIG. 8. In this case the IR laser and/or
the UV/vis source can be used to thermally desorb material from a
sample and then the desorbed material may be analyzed in a mass
spectrometer. In FIG. 8, light from IR source 800 or UV/vis source
812 can be focused onto sample 806 with objective 804. The focused
intensity of the selected laser source is set to be sufficient to
desorb and/or vaporize material from the sample 806. At least a
portion of the desorbed plume is collected by collection tube 808
which then transfers the desorbed material to a mass spectrometer
810 for analysis. The mass spectrometer 810 can then analyze the
chemical content of the desorbed material by creating a spectrum of
the masses of desorbed molecules. The sample can be scanned under
the desorbing beam by scanner 808 to create either an array of mass
spectra or an image at a selected mass. As described previously,
the IR beam in combination with the UV/vis readout can also measure
IR and/or Raman spectra of the same region. Specifically, the IR
light from source 800 is focused on the sample 806 and the
resulting photothermal distortion can be read out with a UV/visible
beam and/or by AFM probe 814. The UV/vis light is collected by
objective 804 and directed to receiver 816 which can comprise a
UV/vis detector, spectrometer or both, as described above. The
UV/vis measurements of the photothermal distortion of the sample
provides a very quick and efficient means to perform an IR survey
scan of the sample to choose areas for analysis by thermal
desorption mass spectrometry. Together this platform can provide
any combination of AFM, IR spectroscopy, laser scanning confocal
microscopy, Raman spectroscopy and mass spectrometry. Using
variable wavelength or broadband UV/visible sources it is also
possible to perform UV/vis spectroscopy as well.
[0045] FIG. 9 shows an embodiment employing total internal
reflection illumination of the infrared radiation. A beam of IR
radiation 900 is focused to pass through an infrared transparent
substrate 902, for example a prism. A sample 904 is mounted or
deposited on the prism 902. The illumination angle of beam 900 is
chosen to provide total internal reflection at the upper surface of
the prism 902. In this case the sample may be illuminated only when
the index of refraction is sufficient to allow transmission into
the sample or by evanescent fields that propagate into the sample.
Reflected beam 906 can be analyzed by an IR detector to provide
spectroscopic characterization of the sample down to the scale of a
spatial resolution limited by diffraction limit of the incoming
beam 900. Sub-diffraction limited measurements of IR absorption can
be made using a probe of a probe microscope 908 and/or a UV/visible
beam from optical source 910, as described previously. The light
from UV/vis source 910 is focused by objective 912 and
reflected/scattered light can be collected by the same objective.
At least a portion of the collected light is directed towards
received 914 which can comprise a UV/vis detector, a spectrometer,
or both. Because of the evanescent illumination, the IR beam can
have a very limited penetration depth into the sample, providing
improved surface sensitivity, specifically to the surface closest
to the IR transparent prism 902.
[0046] The embodiments described herein are exemplary.
Modifications, rearrangements, substitute processes, alternative
elements, etc. may be made to these embodiments and still be
encompassed within the teachings set forth herein. One or more of
the steps, processes, or methods described herein may be carried
out by one or more processing and/or digital devices, suitably
programmed.
[0047] Depending on the embodiment, certain acts, events, or
functions of any of the method steps described herein can be
performed in a different sequence, can be added, merged, or left
out altogether (e.g., not all described acts or events are
necessary for the practice of the algorithm). Moreover, in certain
embodiments, acts or events can be performed concurrently, rather
than sequentially.
[0048] The various illustrative logical blocks, optical and SPM
control elements, and method steps described in connection with the
embodiments disclosed herein can be implemented as electronic
hardware, computer software, or combinations of both. To clearly
illustrate this interchangeability of hardware and software,
various illustrative components, blocks, modules, and steps have
been described above generally in terms of their functionality.
[0049] Whether such functionality is implemented as hardware or
software depends upon the particular application and design
constraints imposed on the overall system. The described
functionality can be implemented in varying ways for each
particular application, but such implementation decisions should
not be interpreted as causing a departure from the scope of the
disclosure.
[0050] The various illustrative logical blocks and modules
described in connection with the embodiments disclosed herein can
be implemented or performed by a machine, such as a processor
configured with specific instructions, a digital signal processor
(DSP), an application specific integrated circuit (ASIC), a field
programmable gate array (FPGA) or other programmable logic device,
discrete gate or transistor logic, discrete hardware components, or
any combination thereof designed to perform the functions described
herein. A processor can be a microprocessor, but in the
alternative, the processor can be a controller, microcontroller, or
state machine, combinations of the same, or the like. A processor
can also be implemented as a combination of computing devices,
e.g., a combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0051] The elements of a method, process, or algorithm described in
connection with the embodiments disclosed herein can be embodied
directly in hardware, in a software module executed by a processor,
or in a combination of the two. A software module can reside in RAM
memory, flash memory, ROM memory, EPROM memory, EEPROM memory,
registers, hard disk, a removable disk, a CD-ROM, or any other form
of computer-readable storage medium known in the art. An exemplary
storage medium can be coupled to the processor such that the
processor can read information from, and write information to, the
storage medium. In the alternative, the storage medium can be
integral to the processor. The processor and the storage medium can
reside in an ASIC. A software module can comprise
computer-executable instructions which cause a hardware processor
to execute the computer-executable instructions.
[0052] Conditional language used herein, such as, among others,
"can," "might," "may," "e.g.," and the like, unless specifically
stated otherwise, or otherwise understood within the context as
used, is generally intended to convey that certain embodiments
include, while other embodiments do not include, certain features,
elements and/or states. Thus, such conditional language is not
generally intended to imply that features, elements and/or states
are in any way required for one or more embodiments or that one or
more embodiments necessarily include logic for deciding, with or
without author input or prompting, whether these features, elements
and/or states are included or are to be performed in any particular
embodiment. The terms "comprising," "including," "having,"
"involving," and the like are synonymous and are used inclusively,
in an open-ended fashion, and do not exclude additional elements,
features, acts, operations, and so forth. Also, the term "or" is
used in its inclusive sense (and not in its exclusive sense) so
that when used, for example, to connect a list of elements, the
term "or" means one, some, or all of the elements in the list.
[0053] Disjunctive language such as the phrase "at least one of X,
Y or Z," unless specifically stated otherwise, is otherwise
understood with the context as used in general to present that an
item, term, etc., may be either X, Y or Z, or any combination
thereof (e.g., X, Y and/or Z). Thus, such disjunctive language is
not generally intended to, and should not, imply that certain
embodiments require at least one of X, at least one of Y or at
least one of Z to each be present.
[0054] The terms "about" or "approximate" and the like are
synonymous and are used to indicate that the value modified by the
term has an understood range associated with it, where the range
can be .+-.20%, .+-.15%, .+-.10%, .+-.5%, or .+-.1%. The term
"substantially" is used to indicate that a result (e.g.,
measurement value) is close to a targeted value, where close can
mean, for example, the result is within 80% of the value, within
90% of the value, within 95% of the value, or within 99% of the
value.
[0055] Unless otherwise explicitly stated, articles such as "a" or
"an" should generally be interpreted to include one or more
described items. Accordingly, phrases such as "a device configured
to" are intended to include one or more recited devices. Such one
or more recited devices can also be collectively configured to
carry out the stated recitations. For example, "a processor
configured to carry out recitations A, B and C" can include a first
processor configured to carry out recitation A working in
conjunction with a second processor configured to carry out
recitations B and C.
[0056] While the above detailed description has shown, described,
and pointed out novel features as applied to illustrative
embodiments, it will be understood that various omissions,
substitutions, and changes in the form and details of the devices
or methods illustrated can be made without departing from the
spirit of the disclosure. As will be recognized, certain
embodiments described herein can be embodied within a form that
does not provide all of the features and benefits set forth herein,
as some features can be used or practiced separately from others.
All changes which come within the meaning and range of equivalency
of the claims are to be embraced within their scope.
* * * * *